Heat stress causes significant economic losses in animal industries, such as dairy industries. Production, reproduction and animal health are impaired by hyperthermia. Physiological and production responses are well documented, but not fully understood. During heat stress, respiration rates and body temperatures increase, and feed intake, milk yield, and reproduction decrease.
Milk synthesis decreases from reduced feed intake. There are additional losses in milk yield that are associated metabolic changes (Rhoads et al., 2009). Countering the production effects of heat stress in lactating dairy cows involves reduced maintain feed intake and controlling metabolic flux.
Immune function and health are also reduced with heat stress. The severity and occasion of disease are increased when immune and inflammatory responses are impaired. The rumen environment can be altered during thermal stress. Increased respiration rates can cause respiratory alkalosis, rumen acidosis and eventually metabolic acidosis. Oxidative stress can be increased with heat stress and can impair the heat shock response and increase cell damage and death.